Verse 2.12.1

अभिमन्थति स हिंकारो धूमो जायते स प्रस्तावो ज्वलति स उद्गीथोऽङ्गारा भवन्ति स प्रतिहार उपशाम्यति तन्निधनं संशाम्यति तन्निधनमेतद्रथंतरमग्नौ प्रोतम् ॥ २.१२.१ ॥

abhimanthati sa hiṃkāro dhūmo jāyate sa prastāvo jvalati sa udgītho'ṅgārā bhavanti sa pratihāra upaśāmyati tannidhanaṃ saṃśāmyati tannidhanametadrathaṃtaramagnau protam || 2.12.1 ||

1. When one rubs two pieces of wood against each other to light a fire, that is the hiṃkāra. When it produces smoke, that is the prastāva. Then when the flame appears, that is the udgītha. The charcoals that result are the pratihāra, and when the fire begins to go out, that is the nidhana. When the flame is completely extinguished, that also is the nidhana. This Sāma called Rathantara is rooted in fire.

Word-for-word explanation:

Abhimanthati, rubbing [one piece of wood against another to produce fire]; saḥ hiṃkāraḥ, that is the hiṃkāra; dhūmaḥ jāyate, the smoke it produces; saḥ prastāvaḥ, that is the prastāva; jvalati, the flames that appear; saḥ udgīthaḥ, that is the udgītha; aṅgārāḥ bhavanti, the charcoals that result; saḥ pratihāraḥ, that is the pratihāra; upaśāmyati, when the fire begins to go out; tat nidhanam, that is the nidhana; saṃśāmyati, when the fire is completely extinguished; tat nidhanam, that [also] is the nidhana; etat rathantaram, this [Sāma] called Rathantara; agnau protam, is rooted in fire.

Commentary:

The rubbing of two pieces of wood together to produce fire is the hiṃkāra, for that is the beginning of the fire. And the smoke that results is the prastāva, for both are likely to continue. When the fire bursts into flame, that is the udgītha, because when there are flames the oblations are offered into them for the gods and goddesses. This is why this part is superior and why the flames are called the udgītha. The charcoals that are formed are called the pratihāra, for the charcoals are collected for future use. Upaśām means the process of subsiding—that is, the fire begins to subside but does not quite go out. Then the word saṃśām means ‘completely extinguished.’ The fire is then dead, so it is like the nidhana (death).

The Rathantara Sāma is said to be based on fire, for when fire is being produced by rubbing the two sticks, the Rathantara Sāma is recited.